In farming operations, the use of fertilizer to enhance crop yields has been known for many years. In an effort to make the use of fertilizer more efficient, new types of fertilizer have also been developed over the years. As the use of fertilizer increased and as new types were developed, mechanization for application of the fertilizer had to be developed and then improved.
While mechanization for application of some types of fertilizer did not prove to be overly difficult, mechanization for application of other types of fertilizer such as, for example, application of chemical fertilizers in liquid-gaseous form, proved to be more difficult and a completely satisfactory apparatus has not heretofore been developed for this purpose in many cases.
With respect to chemical fertilizers of the liquid-gaseous form, anhydrous ammonia is now most typically utilized in farming operations. Anhydrous ammonia in its natural state is a gas. Upon sufficient pressure, however, anhydrous ammonia turns to a liquid and it is in this form that anhydrous ammonia is stored until being inserted into the soil for fertilizing purposes.
Apparatus has heretofore been developed and/or utilized for inserting chemical fertilizer such as anhydrous ammonia into the soil. Typical of such apparatus is apparatus that includes a knife for cutting rather deeply into the soil with the anhydrous ammonia being inserted at the back of the knife. Such a knife is shown, for example, in U.S. Pat. Nos. 3,605,657 and 3,863,842.
One of the problems associated with application of anhydrous ammonia is that the gaseous form of anhydrous ammonia can easily escape from a furrow and when this occurs, there is, of course, no useful fertilizer deposit. Applicators have been developed with a view toward retaining the gaseous state anhydrous ammonia in the furrow, but such applicators have not proved to be completely successful, at least in some respects. Examples of applicators having elements to cover applied fertilizer are shown in U.S. Pat. Nos. 2,849,969; 3,157,139; 3,227,226; 3,536,145; 3,605,657; 3,707,132; 3,854,429; and 3,863,842.
A sweep type of applicator for anhydrous ammonia has also been heretofore suggested. Examples of the use of such a sweep are shown by U.S. Pat. Nos. 2,842,077 and 3,038,424. While the sweep type applicator was modified in an attempt to maintain the anhydrous ammonia in the formed channel, this type of applicator has also not proved to be completely satisfactory for anhydrous ammonia applications and could be improved if better retention of the anhydrous ammonia in the formed channel could be achieved.